Patients on hemodialysis (HD) exhibit an immensely increased cardiovascular mortality associated with extensive vascular calcification (VC). In the past years the development of VC was discovered to be actively regulated and as being influenced by inhibitors of calcification (e.g. matrix-Gla-protein, fetuin-A). MGP is produced by vascular smooth muscle cells and needs post-translational modification by vitamin K dependent gamma-carboxylation to be fully active. Based on the demonstration of increased PIVKA-II levels, about 97% of all HD patients exhibit insufficient carboxylation activity. We therefore aim in this randomized, controlled study to retard the progress of coronary and aortal calcification as assessed by thoracic multislice-CT by the thrice weekly administration of 5 mg vitamin K1 (phylloquinone) to about 100 HD patients over a period of 18 months.